tests: remove non-working and unused tests for state IO

[hkershaw-brown]

Description:

Removes IO dev tests.
Not used, out-of-date, or do not run (#106)

Fixes issue

fixes #106 (removes dead code)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Removes dead code

Documentation changes needed?

• My change requires a change to the documentation.
  • I have updated the documentation accordingly.

Tests

Please describe any tests you ran to verify your changes.
Built everything in dart to to confirm nothing is using the io test code:
https://github.com/NCAR/DART/actions/runs/12162207342
(note GOES failing is rttov 13 not in the container: NCAR/DART-containers#1)

Checklist for merging

• Updated changelog entry
• Documentation updated
• Update conf.py

Checklist for release

• Merge into main
• Create release from the main branch with appropriate tag
• Delete feature-branch

Testing Datasets

• Dataset needed for testing available upon request
• Dataset download instructions included
• No dataset needed

[mjs2369]

Clean removal, approved